Toner supplying apparatus and image forming apparatus

FIELD OF THE INVENTION AND RELATED ART

0001The present invention relates to a toner supplying apparatus employed by a copying machine, a printer, a facsimileing machine, etc., which form an image with the use of an electrophotographic or electrostatic recording method. It also relates to an image forming apparatus.

0002As the developing method employed by such an image forming apparatus as the abovementioned ones, the following method has been known: Dry developer as developing agent is borne on the peripheral surface of a developer bearing member (developing means), and is delivered by the developer bearing member to the immediate adjacencies of the peripheral surface of an image bearing member, which is bearing an electrostatic latent image, so that as alternating voltage is generated between the image bearing member and developer bearing member, the electrostatic latent image is developed into a visible image. It has been a common practice to use a development sleeve and a photosensitive drum as the developer bearing member and image bearing member, respectively.

0003As for the developing means, the so-called magnetic brush type developing method has been known. According to this method, a development sleeve and a photosensitive drum are positioned so that there is a minute gap between their peripheral surfaces, and a magnetic brush is formed of two-component developer (primary components of which are particulate carrier and particulate toner), on the peripheral surface of a development sleeve which internally holds a magnet, and so that the tip of the magnetic brush rubs, or virtually rubs, the peripheral surface of the photosensitive drum. Then, alternating electric field is continuously generated across the gap (S-D gap) between the development sleeve and photosensitive drum so that the latent image on the peripheral surface of the photosensitive drum is developed while the toner particles oscillate between the development sleeve and photosensitive drum (for example, Japanese Laid-open Patent Applications 55-32060, and 59-165082).

0004Next, the structure of a developing apparatus employing one of the two-component magnetic brush based developing methods will be described. Referring to <figref idref="DRAWINGS">FIG. 5</figref> which is a sectional view of an example of a developing apparatus of this type, at a plane perpendicular to the lengthwise direction thereof, the developing apparatus <b>100</b> comprises: a development sleeve <b>101</b> as a developer bearing member used for developing an electrostatic image formed on an image bearing member; a magnetic roller <b>102</b> as a magnetic field generating means stationarily placed in the hollow of the development sleeve <b>101</b>; a development screw <b>103</b> and a stirring screw <b>104</b> as means for conveying the developer in the developing apparatus <b>100</b> to the development sleeve <b>101</b> while stirring it; developing means container <b>105</b> comprising a toner reception hole <b>105</b><i>a</i>, a development chamber <b>105</b><i>b</i>, and a stirring chamber <b>105</b><i>c</i>; and a regulation blade <b>106</b> as a developer regulating member provided for forming a thin uniform layer of developer on the peripheral surface of the development sleeve <b>101</b>. Located on top of the developing apparatus <b>100</b> is a toner container <b>200</b> as a container for holding the toner supply for the developing apparatus <b>100</b>. The toner container <b>200</b> is connected to the abovementioned toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b>. The toner container <b>200</b> is provided with a toner conveyance screw <b>205</b> as a conveying means for delivering toner from the toner container <b>200</b> to the developing apparatus <b>100</b>. As will be evident from the drawing, the development sleeve <b>101</b> is positioned very close to the photosensitive drum <b>111</b> as an image bearing member to be developed, and is rotated in the direction opposite to, or the same as, the rotational direction of the photosensitive drum <b>111</b>, so that the latent image on the peripheral surface of the photosensitive drum <b>111</b> is developed by the developer (represented by dots) in the magnetic brush, which is in contact with the peripheral surface of the photosensitive drum <b>111</b>.

0005The developing means container <b>105</b> contains developer (two-component developer), which primarily is a mixture of particulate toner and particulate magnetic carrier. As the toner in the developing means container <b>105</b> is consumed by development, the toner supply in the toner container <b>200</b> is conveyed from the toner container <b>200</b> to the developing means container <b>105</b> by the toner conveyance screw <b>205</b>, by the amount matching the amount of the toner consumed by development. As the toner is delivered to the toner reception hole <b>105</b><i>a </i>of the developing means container <b>105</b>, it falls through the hole <b>105</b><i>a </i>into the stirring chamber <b>105</b><i>c </i>having the stirring screw <b>104</b>.

0006Thus, the ratio of particulate toner to magnetic carrier (which hereinafter will be referred to as “T/C ratio”) remains constant. As for the method for detecting the T/C ratio in the developing means container <b>105</b> and maintaining it at a predetermined value, various methods have been proposed, and some of them have been put to practical use.

0007For example, according to one of such methods, a T/C ratio detecting means is placed in the adjacencies of the photosensitive drum <b>111</b>, and a beam of light is projected onto the layer of the toner having transferred from the development sleeve <b>101</b> onto the photosensitive drum <b>111</b>. Then, the amount by which toner is supplied is adjusted from the amount of the transmitted light and the amount of the reflected light, in order to maintain the T/C ratio at a predetermined level. According to another method, a detecting means is placed on the development sleeve <b>101</b>, and the T/C ratio is deduced from the amount of the light reflected when a beam of light is projected onto the layer of developer on the development sleeve <b>101</b>. According to another method, a sensor is located within the developing means container <b>105</b>, and the changes in the apparent permeability μ of the body of developer, with a predetermined volume, in the adjacencies of the sensor are detected based on the inductance of a coil in order to detect the T/C ratio. Then, the T/C ratio is deduced from the detected changes.

0008In the case if the above-described method in which a toner content detection sensor based on the changes in the permeability of a body of developer with a predetermined volume, the increase in permeability means the decrease in the T/C ratio of the body of developer with a predetermined volume, in other words, the decrease in the toner content in the developer. Thus, as the permeability increases beyond a preset value, the toner supplying operation is started. On the other hand, the decrease in the permeability means the increase in the T/C ratio in the body of developer with a predetermined volume, in other words, the increase in the toner content in the developer. Thus, as the permeability decreases below a preset value, the toner supplying operation is stopped. In other words, the T/C ratio is controlled by alternately repeating the above-described sequences.

0009Referring to <figref idref="DRAWINGS">FIG. 6</figref> which is a plan view of the developing apparatus <b>100</b>, the development sleeve <b>101</b>, development screw <b>103</b>, and stirring screw <b>104</b> are rotationally driven by the force transmitted from a driving force source (unshown) such as a motor through a driving force transmitting means (unshown) such as a gear train. As the development screw <b>103</b> and stirring screw <b>104</b> are rotated in a predetermined direction at a predetermined speed, the developer in the developing means container <b>105</b> is circulated therein in the direction indicated by an arrow mark. In other words, as the fresh supply of toner is delivered through the toner reception hole <b>105</b><i>a</i>, it is conveyed through the stirring chamber <b>105</b><i>b</i>, while being evenly distributed in the developer and being thoroughly charged by friction. Then, it is delivered to the development chamber <b>105</b><i>b</i>. In the development chamber <b>105</b><i>b</i>, a magnetic brush is formed of the developer, on the peripheral surface of the development sleeve <b>101</b> by the development magnetic field generated by the magnetic roller <b>102</b> in the hollow of the development sleeve <b>101</b>, and the toner particles adhering to the magnetic brush and the toner particles adhering to the peripheral surface of the development sleeve <b>101</b> transfer onto the area of the peripheral surface of the photosensitive drum <b>111</b> bearing the electrostatic latent image, developing thereby the image.

0010Next, referring to <figref idref="DRAWINGS">FIG. 7</figref> which is a sectional view of a typical toner supplying apparatus <b>300</b> in accordance with the prior art, at a vertical plane which is parallel with the lengthwise direction of the developing apparatus <b>100</b>, the toner supplying apparatus <b>300</b> comprises: a toner container <b>200</b> as a toner supply container comprising a main chamber <b>201</b> and a buffer chamber <b>202</b>; a pipe <b>203</b> as a toner conveyance passage; a toner discharge hole <b>204</b> (toner drop hole); a toner conveyance screw <b>205</b> as a toner conveying member; a driving means <b>206</b> for rotationally driving the toner conveyance screw <b>205</b>; a drive controlling means <b>207</b> for controlling the driving or stopping of the driving means <b>206</b>; a toner supply amount computing means <b>214</b> which determines the amount by which toner is to be supplied to the developing apparatus <b>100</b>, based on the programs and data stored in a storage device <b>215</b>, and outputs to the drive controlling means <b>207</b>, the number of rotations or length of time necessary for the toner conveyance screw <b>205</b> to be rotated to deliver toner by the determined amount; and a developing apparatus <b>100</b> (developing means container <b>105</b>) as a toner receiver, which catches the toner discharged downward from the pipe <b>203</b>.

0011The developing apparatus <b>100</b> is removably attached to the image forming apparatus main assembly, being enabled to move relative to the main assembly of the toner supplying apparatus <b>300</b>. More specifically, the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b> is connected to the abovementioned toner discharge hole <b>204</b> of the toner container <b>200</b>. Among the above listed structural components, only the developing apparatus <b>100</b> is an replaceable component (exchangeable unit) that can be removably mountable in the main assembly of an image forming apparatus, being enabled to be removably connected to the toner supplying apparatus. The other components are non-replaceable structural components of the apparatus main assembly.

0012The main chamber <b>201</b> of the toner container <b>200</b> stores the toner filled therein by a user or such an operator as the maintenance person of the apparatus. The main chamber <b>201</b> contains a stirring member (unshown), which sends toner to the buffer chamber <b>202</b>, as necessary, while stirring the toner to prevent the toner from agglomerating. The bottom end of the buffer chamber <b>202</b> is connected to the pipe <b>203</b>, which is provided with the toner discharge outlet <b>204</b>, which is located near the tip of the pipe <b>203</b>, extending vertically downward, and through which the toner is allowed to fall.

0013Within the pipe <b>203</b>, the toner conveyance screw <b>205</b>, which comprises a rotational shaft and a spiral flange attached to the rotational shaft, is rotatably supported. As the toner conveyance screw <b>205</b> is rotated, the toner in the pipe <b>203</b> is advanced in the direction in which the rotating spiral flange appears to advance as it is rotated. More specifically, the toner conveyance screw <b>205</b> is rotated or stopped by controlling the driving means <b>206</b> with the use of the drive controlling means <b>207</b>. As the toner reaches the toner discharge hole <b>204</b>, it falls through the toner discharge hole <b>204</b> due to its own weight, into the developing apparatus <b>100</b> through the toner reception hole <b>105</b><i>a</i>; the developing apparatus <b>100</b> is supplied with toner.

0014The toner supply amount computing means <b>214</b> determines the amount by which toner is to be supplied to the developing apparatus <b>100</b>, based on the values of the outputs of the sensor for detecting the ratio of the toner in the developer, and data such as print density and cumulative amount of the supplied toner, stored in the storage device <b>215</b>. Based on the determined amount, the toner amount computing means <b>214</b> outputs to the drive controlling means <b>207</b>, the number of times, or length of time, the toner conveyance screw <b>205</b> needs to be rotated. As a result, the toner conveyance screw <b>205</b> is rotationally driven the necessary number of times, or length of time, conveying thereby the toner to supply the developing apparatus <b>100</b> with the toner.

0015The number of times, or length of time, the toner conveyance screw <b>205</b> is to be rotated is determined based on the amount determined by the toner supply amount computing means <b>214</b>. As the toner conveyance screw <b>205</b> it is rotated the necessary number of times, or length of time, it is stopped so that the toner is supplied only by the necessary amount to the developing apparatus <b>100</b> through the toner discharge hole <b>204</b>.

0016The amount by which toner is conveyed by the toner conveyance screw <b>205</b> per rotation of the toner conveyance screw <b>205</b>, or per unit of time, is numerated and stored in the storage device <b>215</b>, so that it can be read as necessary by the toner supply amount computing means <b>214</b> to compute the number of times, or length of time, the toner conveyance screw <b>205</b> is to be rotated. Incidentally, the amount by which toner is conveyed by the toner conveyance screw <b>205</b> is roughly proportional to the number of the rotations of the toner conveyance screw <b>205</b>. Therefore, when controlling the amount by which toner is conveyed by the toner conveyance screw <b>205</b>, by controlling the length of time the toner conveyance screw <b>205</b> is rotated, it is mandatory that the means for rotationally driving the toner conveyance screw <b>205</b> is capable of rotating the toner conveyance screw <b>205</b> at a constant speed. However, if a means for counting the rotations of toner conveyance screw <b>205</b> is provided, the amount by which toner is conveyed can be controlled based on the number of the rotations of the toner conveyance screw <b>205</b> even if the rotational speed of the toner conveyance screw <b>205</b> is not constant.

0017The location of the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b> in terms of the lengthwise direction of the developing apparatus <b>100</b> is chosen so that the received toner is sufficiently stirred and mixed with the developer in the developing apparatus <b>100</b>, and also so that the received toner is thoroughly charged. More specifically, moving the toner reception hole <b>105</b><i>a </i>too far in the direction indicated by an arrow mark A causes the problem that the uncharged toner back-flows toward the development chamber <b>105</b><i>b</i>. On the other hand, moving the toner reception hole <b>105</b><i>a </i>too far in the direction indicated by an arrow mark B creates the problem that the toner fails to be sufficiently charged by the time it reaches the development chamber <b>105</b><i>b</i>. Thus, the toner reception hole <b>105</b><i>a </i>must be located within the limited range in terms of the developing apparatus <b>100</b>, making it therefore necessary for the toner reception hole <b>105</b><i>a </i>to be located a certain distance away from the buffer chamber <b>202</b> of the toner container <b>200</b> in the horizontal direction. This is why the toner conveyance screw <b>205</b> is given the function of horizontally conveying toner from the buffer chamber <b>202</b> of the toner container <b>200</b> to the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b>.

0018As described above, according to the prior art, the toner conveyance screw <b>205</b> as a toner conveying member is given two functions: the function of precisely controlling the amount by which toner is supplied, by its rotation, and the function of horizontally conveying toner to the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b>.

0019In other words, according to the prior art, toner is conveyed and let fall through the toner discharge hole <b>204</b>, by rotating the toner conveyance screw <b>205</b> the number of times proportional to the amount of the toner required by the developing apparatus <b>100</b>. Thus, immediately after the rotation of the toner conveyance screw <b>205</b> is stopped, toner is present immediately next to the toner discharge hole <b>204</b> (point X in <figref idref="DRAWINGS">FIG. 7</figref>). Therefore, as soon as the rotation of the toner conveyance screw <b>205</b> is started, toner begins to fall. Thus, the amount by which toner is conveyed is virtually proportional to the number of the rotations of the toner conveyance screw <b>205</b>, making it possible to precisely control the amount by which the developing apparatus <b>100</b> is supplied with toner.

0020However, in the case of this structural arrangement, when mounting or dismounting the developing apparatus <b>100</b>, which is a unit removably mountable in the main assembly of an image forming apparatus, a small amount of toner falls due to vibrations, no matter how small the vibrations are. Therefore, both the toner outlet <b>204</b> of the toner supply container <b>200</b> and the toner reception hole <b>105</b><i>a </i>has to be provided with a complicated shutter mechanism.

0021Obviously, it is extremely difficult to perfectly prevent toner from scattering, by the provision of the shutters. That is, in the case of the toner supplying apparatus in accordance with the prior art, in which toner is present immediately next to the toner discharge hole <b>204</b>, through which toner is supplied to the developing apparatus <b>100</b>, the provision of the shutter mechanisms is mandatory. However, even if these shutter mechanisms are provided, it is impossible to avoid the problem that a small amount of toner scatters during the mounting or dismounting of the developing apparatus <b>100</b>. This scattering of toner has been one of the essential causes of the soiling of the operator's hands, dirtying of the surroundings, and/or degradation of the image forming apparatus.

0022Also in the case of this structural arrangement, it is possible that when the toner conveyance screw <b>205</b> is rotated for only a short length of time to supply the developing apparatus <b>100</b> with toner, the amount by which toner is supplied does not become stable, causing thereby the toner content (toner ratio) in the stirring chamber <b>105</b><i>c </i>to become extremely high in certain areas.

0023As long as developer reaches the development chamber <b>105</b><i>b </i>after it became uniform in toner content in the stirring chamber <b>105</b><i>c</i>, there will be no problem. However, if the mixture of the freshly supplied toner and the developer which was in the stirring chamber <b>105</b><i>c </i>fails to be sufficiently stirred, and reaches the development chamber <b>105</b><i>b </i>before it becomes uniform in toner content, an image which is not uniform in density is formed. In order to solve this problem that the mixture of the fresh supply of toner and the developer which was in the developing apparatus <b>100</b> fails to be sufficiently stirred, and therefore, fails to become uniform in toner content, it is important that toner is supplied at a lower rate, and a sufficient amount of time is provided for stirring the mixture, to minimize the nonuniformity of the developer in the stirring chamber <b>105</b><i>b </i>in terms of toner content. This solution, however, contradicts the effort for reducing the time necessary for image formation. In recent years, this contradiction has become one of the largest technical problems, because the desire to increase the speed of an image forming apparatus has become extremely strong in recent years.

SUMMARY OF THE INVENTION

0024The primary object of the present invention is to provide a toner supplying apparatus which does not scatter toner when mounting or dismounting an apparatus having a toner chamber (third chamber) into which toner is discharged from the toner supply container.

0025Another object of the present invention is to provide a toner supplying apparatus capable of preventing the toner content in a developing device from locally increasing to an extremely high level even if a large amount of toner is discharged from the first toner chamber of the toner supplying apparatus.

0026These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0027<figref idref="DRAWINGS">FIG. 1</figref> is a schematic sectional view of the toner supply container in the first embodiment of the present invention.

0028<figref idref="DRAWINGS">FIG. 2</figref> is a timing chart for describing the toner supplying operation in accordance with the present invention.

0029<figref idref="DRAWINGS">FIG. 3</figref> is a schematic sectional view of a typical image forming apparatus in accordance with the present invention.

0030<figref idref="DRAWINGS">FIG. 4</figref> is a schematic sectional view of the toner supplying apparatus in another embodiment of the present invention.

0031<figref idref="DRAWINGS">FIG. 5</figref> is a schematic sectional view of an example of a developing apparatus in accordance with the prior art.

0032<figref idref="DRAWINGS">FIG. 6</figref> is a schematic plan view of an example of a developing apparatus in accordance with the prior art.

0033<figref idref="DRAWINGS">FIG. 7</figref> is a schematic sectional view of an example of a toner supplying apparatus in accordance with the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0034Hereinafter, the toner supplying apparatuses in accordance with the present invention will be described in more detail with reference to the appended drawings.

Embodiment 1

0035Referring to <figref idref="DRAWINGS">FIG. 1</figref>, a typical image forming apparatus which employs a toner supplying apparatus in accordance with the present invention, will be described regarding its general structure. In this embodiment, the present invention is embodied in the form a toner supplying apparatus employable by such an image forming apparatus as an electrophotographic copying machine, a laser printer, a facsimile machine, etc. However, this embodiment is not intended to limit the scope of the present invention in terms of the apparatus to which the present invention is applicable. It should be understood that the present invention is applicable to a wide range of electrophotographic and electrostatic image forming apparatuses.

0036The image forming apparatus <b>110</b> has an electrophotographic photosensitive member <b>111</b> (photosensitive drum) as an image bearing member in the form of a rotational drum. The photosensitive drum <b>111</b> is rotated in the direction indicated by an arrow mark while being uniformly charged by a primary charging device <b>112</b> as a charging means. Thereafter, the charged area of the peripheral surface of the photosensitive drum <b>111</b> is exposed to a beam of laser light projected from an exposing apparatus <b>113</b> (laser scanner) as an exposing means, while being oscillated in a manner to scan the charge area and being modulated with the image formation data signals for a desired image, sent from an external host apparatus such as an original reading apparatus, a personal computer, etc., connected to the main assembly of the image forming apparatus in a manner to allow two-way communication. As a result, an electrostatic latent image in accordance with the image formation data signals is formed on the peripheral surface of the photosensitive drum <b>111</b>. This electrostatic latent image is developed in reverse (in this embodiment) by the developing apparatus <b>100</b>, which uses two-component developer, that is, the mixture of particulate toner and particulate carrier, into a visible image (image formed of toner, which hereinafter will be referred to simply as toner image).

0037Then, the toner image on the peripheral surface of the photosensitive drum <b>111</b> is transferred by the function of a transfer charging device <b>114</b><i>a </i>as a transferring means, onto a transfer medium S held on a transfer medium conveying endless belt <b>114</b><i>b </i>as a transfer medium bearing member, which is suspended by a pair of rollers <b>114</b><i>c </i>and <b>114</b><i>d </i>and is circularly driven.

0038After the transfer of the toner image onto the transfer medium S, the transfer medium S is separated from the transfer medium conveying belt <b>114</b><i>b</i>, and is conveyed to an unshown fixing device, in which the toner image is permanently fixed to the transfer medium S. The residual toner, or the toner remaining on the photosensitive drum <b>111</b> after the transfer of the toner image therefrom, is removed by a cleaning means <b>115</b>, which comprises a cleaning blade, or the like, placed in contact with the photosensitive drum <b>111</b>.

0039Incidentally, for the simplification of the description of the image forming apparatus, <figref idref="DRAWINGS">FIG. 3</figref> shows only one of the image forming portions (each of which comprises: a photosensitive drum <b>111</b>, a primary charging device <b>112</b>, an exposing apparatus <b>113</b> emitting a laser beam L onto the photosensitive drum <b>111</b>, a developing apparatus <b>100</b>, etc.). However, in the case of a color image forming apparatus, multiple image forming portions matching, in number, various colors, for example, cyan, magenta, yellow, and black, are placed along the transfer medium conveying range of the transfer medium conveying belt <b>114</b><i>b</i>. In each image forming portion, an electrostatic image representing one of the color components obtained by separating in color the original, is formed on the photosensitive drum <b>111</b>, and is developed by the corresponding developing apparatus which contains the toner corresponding in color to the color component. Then, the developed latent image, or the toner image, is transferred onto the transfer medium S being conveyed by the transfer medium conveying member <b>114</b><i>b</i>. This image formation process comprising the above described steps is carried out by all the image forming stations in synchronism with the movement of the transfer medium S. Thus, multiple toner images different in colors are sequentially transferred onto the transfer medium S. Incidentally, instead of employing the transferring member bearing member, one of the so-called intermediary transfer systems well known in the field of image formation may be used, which employs an intermediary transferring member (intermediary transfer belt, or the like). In such a case, the toner images formed in the multiple image forming portions, one for one, are sequentially and temporarily transferred in layers onto the intermediary transferring member, and then, are transferred all at once from the intermediary transferring member to the transfer medium S.

0040The developing apparatus <b>100</b> in this embodiment is not different from the above described one in accordance with the prior art. Next, the toner supplying apparatus <b>30</b> in this embodiment, which characterizes the present invention, will be described.

0041<figref idref="DRAWINGS">FIG. 1</figref> is a sectional view of the toner supplying apparatus <b>30</b>, at a plane parallel to the lengthwise direction of the developing apparatus <b>100</b>. As will be evident from <figref idref="DRAWINGS">FIG. 1</figref>, the toner supplying apparatus <b>30</b> comprises: a toner supply container <b>20</b> comprising a main chamber <b>1</b> and a buffer chamber <b>2</b> ; a first pipe <b>3</b> (first toner chamber) as a first toner conveyance passage; a first toner discharge hole <b>4</b> (toner drop hole); a first toner conveyance screw <b>5</b> as a first toner conveying member; a first driving means <b>6</b> for rotationally driving the first toner conveyance screw <b>5</b>; a first drive controlling means <b>7</b> for controlling the driving or stopping of the first driving means <b>6</b>; a second pipe <b>8</b> (second toner chamber) as a second toner conveyance passage; a second toner discharge hole <b>9</b> (toner drop hole); a second toner conveyance screw <b>10</b> as a second toner conveying member; a second driving means <b>11</b> for rotationally driving the second toner conveyance screw <b>10</b>; a second drive controlling means <b>12</b> for controlling the driving or stopping of the second driving means <b>11</b>; a toner supply amount computing means <b>14</b> which determines the amount by which toner is to be supplied to the developing apparatus <b>100</b>, based on the programs and data stored in a storage device <b>15</b>, and outputs to the drive controlling means <b>7</b>, the number of rotations or length of time necessary for the toner conveyance screw <b>5</b> to be rotated to deliver toner by the determined amount; and a developing apparatus <b>100</b> (developing means container <b>105</b>) as a toner receiver, which catches the toner discharged downward through the second toner discharge hole <b>9</b> of the second pipe <b>8</b>. Thus, the first driving means <b>6</b> rotationally drives the first toner conveyance screw <b>5</b> (in response to toner supply signal) by the number of times proportional to the amount by which toner is to be supplied, whereas the second driving means <b>11</b> rotationally drives the second toner conveyance screw <b>10</b> continuously regardless of the amount by which toner is to be supplied.

0042The developing apparatus <b>100</b> is removably attached to the image forming apparatus main assembly, being enabled to move relative to the main assembly of the toner supplying apparatus <b>30</b>. More specifically, the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b> is connected to the above-mentioned second toner discharge hole <b>9</b> of the toner supplying apparatus <b>30</b>. Among the above-listed structural components, only the developing apparatus <b>100</b> is a replaceable component (exchangeable unit) that can be removably mountable in the image forming apparatus main assembly, that is, removably attachable to the main assembly of the toner supplying apparatus. The other components are non-replaceable structural components of the main assembly of the image forming apparatus.

0043The main chamber <b>1</b> stores the toner filled therein by a user or such an operator as the maintenance person of the apparatus, from a toner supply unit (unshown), or the like, removably attachable to the apparatus main assembly. The main chamber <b>1</b> contains a stirring member (unshown), which sends toner to the buffer chamber <b>2</b>, as necessary, while stirring the toner to prevent the toner from agglomerating. The bottom end of the buffer chamber <b>2</b> is connected to the first pipe <b>3</b>, which is provided with the toner discharge outlet <b>4</b>, which is located near the tip of the first pipe <b>3</b>, being open vertically downward, and through which the toner is let fall. The first pipe <b>3</b> is virtually horizontally extended from the buffer chamber <b>2</b> of the toner supply container <b>20</b>.

0044Within the pipe <b>3</b>, the toner conveyance screw <b>5</b> is rotatably supported. As the first toner conveyance screw <b>5</b> is rotated, the toner in the first pipe <b>3</b> is advanced in the direction in which the spiral flange of the first toner conveyance screw <b>5</b> appears to advance as the screw <b>5</b> is rotated. More specifically, the first drive controlling means <b>7</b> controls the first driving means <b>6</b> in order to convey the toner toward the first toner discharge hole <b>4</b>, or stop the first toner conveyance screw <b>5</b> to stop the toner conveyance. As the toner reaches the toner discharge hole <b>4</b>, it falls virtually in its entirety through the toner discharge hole <b>4</b> due to its own weight, into the second pipe <b>8</b>. The second pipe <b>8</b> is roughly horizontally extended from a location below the first toner discharge hole <b>4</b>. It is provided with a second toner discharge hole <b>9</b> through which toner falls due to its own weight, and which is open straight downward.

0045The toner supply amount computing means <b>14</b> determines the amount by which toner is to be supplied to the developing apparatus <b>100</b>, based on the values of the outputs of the sensor for detecting the ratio of the toner in the developer, and data such as print density and cumulative amount of the supplied toner, stored in the storage device <b>15</b>. Then, based on the determined amount, the toner amount computing means <b>14</b> outputs to the first drive controlling means <b>7</b>, the number of times, or length of time, the toner conveyance screw <b>5</b> needs to be rotated. As a result, the toner conveyance screw <b>5</b> is rotationally driven the necessary number of times, or length of time, conveying thereby the toner to cause the toner to fall into the second pipe <b>8</b> through the first toner discharge hole <b>4</b>.

0046The second toner conveyance screw <b>10</b> rotates or stops as the second drive controlling means <b>12</b> controls the second driving means <b>11</b>. Referring to <figref idref="DRAWINGS">FIG. 2</figref>, the timing with which the rotation of the second toner conveyance screw <b>10</b> is started is set by the second drive controlling means <b>12</b> so that the rotation of the second toner conveyance screw <b>10</b> is started no later than when toner begins to be dropped into the second pipe <b>8</b> through the first toner discharge hole <b>4</b>, by the rotation of the first toner conveyance screw <b>5</b> caused by the first driving means <b>7</b>. On the other hand, the timing with which the rotation of the second toner conveyance screw <b>10</b> is stopped is set by the second drive controlling means <b>12</b> so that the second toner conveyance screw <b>10</b> is stopped no earlier than the point in time at which virtually the entirety of the toner in the second pipe <b>8</b> is dropped into the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b> through the second toner discharge hole <b>9</b>, by the rotation of the toner conveyance screw <b>10</b> caused by the second driving means <b>12</b>.

0047In other words, the above-described first and second toner conveyance screws <b>5</b> and <b>10</b> are driven following the above-described control (driving or stopping) sequence, assuring thereby that the amount of the toner which is to be supplied to the developing apparatus <b>100</b> is caused by the first toner conveyance screw <b>5</b> to fall virtually in its entirety into the second pipe <b>8</b> through the first toner discharge hole <b>4</b>, and then, is conveyed virtually in its entirety by the second toner conveyance screw <b>10</b> to the second toner discharge hole <b>9</b>, through which it falls into the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b>. In other words, it is preferable that the second toner conveyance screw <b>10</b> is continuously driven so that the amount of the toner remaining in the second pipe <b>8</b> becomes virtually zero.

0048According to the toner supplying method in this embodiment, toner is dropped into the second pipe <b>8</b> by the first toner conveyance screw <b>5</b> by virtually the exact amount by which toner is to be supplied to the developing apparatus <b>100</b>, and then, is conveyed in its entirety by the second toner conveyance screw <b>10</b> to the location of the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b>. While toner is conveyed through the second pipe <b>8</b>, it sometimes adheres to the internal surface of the second pipe <b>8</b> and the surface of the toner conveyance screw <b>10</b> by a small amount.

0049However, the amount of the toner which adheres to the internal surface of the second pipe <b>8</b> and the surface of the toner conveyance screw <b>10</b> is negligibly small. Therefore, this adhesion of a small amount of toner does not create a serious problem in terms of the toner supplying performance of the toner supplying apparatus, even though toner is not supplied to the developing apparatus <b>100</b> by 100% of the amount by which toner is dropped into the second pipe <b>8</b> by the first toner conveyance screw <b>5</b>.

0050Further, as described above, the rotation of the second toner conveyance screw <b>10</b> is stopped after virtually the entirety of the toner dropped into the second pipe is dropped from the second pipe <b>8</b> into the developing apparatus <b>100</b>. Therefore, there is virtually no toner, except for the toner adhering to the internal wall of the second pipe <b>8</b>, in the adjacencies of the second toner discharge hole <b>9</b>. Therefore, even if the developing apparatus <b>100</b> in the form of an replaceable unit removable relative to the apparatus main assembly, vibrates when mounting or dismounting the developing apparatus <b>100</b>, virtually no toner scatters. Thus, when appearance is not a major concern, or appearance does not matter, it is unnecessary to provide the toner discharge hole <b>9</b> and toner reception hole <b>105</b><i>a </i>with a complicated shutter mechanism. Further, if appearance is a major concern, only the second toner discharge hole <b>9</b> has to be provided with a mechanism for sealing or unsealing the second toner discharge hole <b>9</b>, because the addition of the shutter mechanism for the toner discharge hole <b>9</b> is sufficient to make the image forming apparatus in this embodiment less likely to scatter toner than an image forming apparatus in accordance with the prior art having more complicated shutter mechanisms. As for the choice of the shutter, it may be such a shutter that is mechanically connected to the developing apparatus <b>100</b> as a removably mountable unit so that as the developing apparatus <b>100</b> is mounted or removed, the shutter unseals or seals, respectively, the second toner discharge hole <b>9</b>. According to the present invention, the choice of the shutter is optional; any shutter may be employed as long as long it is capable of sealing or unsealing the second toner discharge hole <b>9</b>. Since the shutter mechanisms of this type are well known in the field of this business, it will not be described in more detail.

0051In this embodiment, the toner supplying operation is controlled as shown in <figref idref="DRAWINGS">FIG. 2</figref>. That is, after the rotation of the second toner conveyance screw <b>10</b> is started (P<b>1</b>), the rotation of the first toner conveyance screw <b>5</b> is started (P<b>2</b>), starting thereby dropping toner through the first toner discharge hole <b>4</b>. Then, after the rotation of the first toner conveyance screw <b>5</b> is stopped (P<b>3</b>), and the falling of the toner through the second toner discharge hole <b>9</b> completely stops (P<b>4</b>), the rotation of the second toner conveyance screw <b>10</b> is stopped (P<b>5</b>).

0052However, even if the rotation of the first toner conveyance screw <b>5</b> is started slightly before the rotation of the second toner conveyance screw <b>10</b> is started, there will be no problem in practical terms as long as toner is conveyed by the second toner conveyance screw <b>10</b> without permanently stagnating, although it may temporarily stagnate.

0053To elaborate, even if the relationship between the rotations of the first and second toner conveyance screws <b>5</b> and <b>10</b>, in terms of the timing with which they are started or stopped, is not as ideal as shown in <figref idref="DRAWINGS">FIG. 2</figref>, in other words, even if the timing with which the rotation of the first toner conveyance screw <b>5</b> is started or stopped is the same as, or slightly earlier or later than, the timing with which the rotation of the second toner conveyance screw <b>10</b> is started or stopped, respectively, toner does not permanently stagnate, as long as the second toner conveyance screw <b>10</b> is superior to the first toner conveyance screw <b>5</b> in terms of toner conveyance performance. In other words, as long as the delay is within the tolerance regarding the performance of the developing apparatus <b>100</b>, effects similar to those obtained when the timings are ideal can be obtained.

0054As described above, even if the chronological relationship between the timings with which the first and second toner conveyance screws <b>5</b> and <b>10</b> are stopped is not as ideal as shown in <figref idref="DRAWINGS">FIG. 2</figref>, as long as the second toner conveyance screw <b>10</b> exceeds in toner conveyance performance the first toner conveyance screw <b>5</b>, toner is supplied to the developing device without permanently stagnating, although there will be a slightly delay in toner delivery compared to when the relationship is ideal.

0055In other words, all that is necessary is that the second driving means <b>11</b> for driving the second toner conveyance screw <b>10</b> is controlled by the second drive controlling means <b>12</b> so that the following inequality is satisfied: N<b>2</b>×T<b>2</b>>N<b>1</b>×T<b>1</b>, wherein N<b>1</b> stands for the amount by which toner is conveyed per driving of the first toner conveyance screw <b>5</b> by the first driving means <b>6</b> (amount of toner conveyed per rotation of screw, or per unit of time); T<b>1</b> stands for the number times the toner conveyance screw <b>5</b> is driven by the first driving means <b>6</b> (number of revolution, or length of rotation); N<b>2</b> stands for the amount by which toner is conveyed per driving of the second toner conveyance screw <b>10</b> by the second driving means <b>11</b> (amount of toner conveyed per rotation of screw, or per unit of time); T<b>2</b> stands for the number times the toner conveyance screw <b>10</b> is driven by the second driving means <b>11</b> (number of revolution, or length of rotation).

0056In this case, such a measure as using each driving force source to drive multiple components may be taken. For example, the toner conveyance screw <b>10</b> may be driven by the driving force source which drives the development screw <b>103</b> and stirring screw <b>104</b> for conveying developer in the developing apparatus <b>100</b>, or the development sleeve <b>101</b>. In reality, the toner conveyance screw <b>10</b> may be always driven while the developing apparatus <b>100</b> is in action.

0057As described above, in the case of a toner supplying apparatus in accordance with the prior art, the two functions of conveying and measuring are performed by a single member, or the toner conveying member. In comparison, the toner supplying portion of an image forming apparatus in this embodiment is provided with the first toner conveying member (first toner conveyance screw <b>5</b>) which functions as a metering device as well as a conveying device, and the second toner conveying member (second toner conveyance screw) which functions simply as a conveying device.

0058In the case of the toner supplying apparatus in this embodiment, therefore, the state in which virtually no toner is present in the adjacencies of the second toner discharge hole <b>9</b>, through which toner is supplied to the developing apparatus <b>100</b>, is realized by the functions of the first and second toner conveying members <b>5</b> and <b>10</b>, reducing as much as possible the toner leakage and scattering which occur at the junction between the second toner discharge hole <b>9</b> of the toner supplying apparatus <b>30</b> and the toner reception hole <b>105</b><i>a </i>of the developing apparatus <b>100</b> (development unit) removably mountable in the main assembly of an image forming apparatus.

0059Also in the case of the toner supplying apparatus in this embodiment, even if toner is delivered in a short time by the first toner conveying member (first toner conveyance screw <b>5</b>) from the first pipe <b>3</b> to the second pipe <b>8</b> in which the second toner conveying member (second toner conveyance screw <b>10</b>) is present, the body of the toner having fallen from the first pipe <b>3</b> does not remain in the same state as that in which it was immediately after it fell from the first pipe <b>3</b>. That is, while it is conveyed by the second toner conveying member (second toner conveyance screw <b>10</b>) through the pipe <b>8</b>, it gradually loosens, disintegrates, and levels, being therefore continuously dropped into the developing apparatus <b>100</b> little by little. In other words, even if toner is delivered in a very short time by the first toner conveying member (first toner conveyance screw <b>5</b>) from the first pipe <b>3</b> to the second pipe <b>8</b> in which the second toner conveying member (second toner conveyance screw <b>10</b>) is present, when it is delivered by the second toner conveying member <b>10</b> (second toner conveyance screw) from the pipe <b>8</b> to the developing apparatus <b>100</b>, it is delivered in a continuous flow at a constant rate into the stirring chamber <b>105</b><i>c </i>of the developing apparatus <b>100</b>. Therefore, it is possible to reduce as much as possible the possibility that the toner content in the developing apparatus <b>100</b> become locally high.

0060The first and second toner conveyance passages, and the first and second toner conveying members, may be of a single piece, or multiple pieces, as long as they are capable of efficiently performing the above described functions, while minimizing the developer leakage and developer scattering which occur at the junction between the toner discharge hole through which toner is delivered (dropped) and the toner reception hole on the side which is to be supplied with toner.

0061In this embodiment, the toner conveying members are in the form of a screw. However, this embodiment is not intended to limit the scope of the present invention in terms of the toner conveying means. In other words, the first or second toner conveying member, or both, may be in the form of something other than a screw, as long as they can efficiently convey toner. For example, even when they are in the form of a belt or the like, the effect of the present invention will be the same as those obtained when they in the form of a screw.

0062Also in this embodiment, the first and second toner conveyance passages as the first and second toner chambers are in the form of a pipe. However, this embodiment is not intended to limit the present invention in terms of the configuration of the first and second toner conveyance passages. For example, the first or second toner conveyance passages, or both, may be in the form of something other than a pipe.

0063For example, referring to <figref idref="DRAWINGS">FIG. 4</figref>, which shows a toner supplying container <b>30</b>′ comprising: a first toner chamber <b>3</b>′; a first toner conveying member <b>5</b> for conveying the toner in the first toner chamber <b>3</b>′; a second toner chamber <b>8</b>′ which receives the toner from the first toner chamber <b>3</b>′; a second toner conveying member <b>10</b> for conveying the toner in the second toner chamber <b>8</b>′; and a development unit <b>100</b> (developing means container <b>105</b>) removably mountable in the image forming apparatus main assembly and having a third toner chamber which receives the toner discharged downward from the second toner chamber <b>8</b>′. When supplying the development unit <b>100</b> with the use of this toner supplying apparatus <b>30</b>′, the first toner conveying member <b>5</b> is driven by the number of times, or length of time, proportional to the amount by which the development unit <b>100</b> is to be supplied with toner. Preferably, the second toner conveying member <b>10</b> is driven in connection with the conveying means <b>103</b> and <b>104</b> for conveying the toner in the development unit <b>100</b>, or the development sleeve <b>101</b>, so that the second toner conveying member <b>10</b> is continuously driven regardless of the amount by which the developing apparatus <b>100</b> is to be supplied with toner. With the employment of this mechanical arrangement, the problem that toner scatters due to the vibrations which occur when the development unit <b>100</b> is mounted into, or dismounted from, the image forming apparatus main assembly, does not occur. However, in order to be more sure that toner is prevented from scattering, the toner supplying apparatus <b>30</b>′ may be provided with a shutter for sealing or unsealing the toner discharge hole <b>9</b> of the second toner chamber <b>8</b>′.

0064The first toner chamber <b>3</b>′ is equivalent to the first chamber of a toner hopper, that is the chamber into which toner is first delivered from the toner supplying unit <b>40</b> removably mountable in the image forming apparatus main assembly, or a toner cartridge itself removably mountable in the main assembly of an image forming apparatus. The second toner chamber <b>8</b>′ is equivalent to the second chamber of a toner hopper, that is, the chamber which receives toner from the first toner chamber <b>3</b>′, or a toner conveyance passage through which toner is conveyed from the first toner chamber <b>3</b>′ to the development unit <b>100</b>.

0065Also in this embodiment, the subordinate apparatus or device (movable unit) which is to be supplied with particulate consumables, and which is movable relative to the main assembly of an apparatus, is a developing apparatus as a replaceable unit removably mountable in the main assembly of an image forming apparatus. However, this embodiment is not intended to limit the scope of the present invention in terms of an apparatus which is to be supplied with particulate consumables. In other words, the present invention is applicable to any apparatus (unit) employing a powder supplying apparatus having a powder reception hole, in order to prevent powder from scattering, and the effect which will be realized by such application will be similar to the effects in this embodiment. For example, the apparatus to be supplied with particulate consumables may be a process cartridge as a replaceable unit, which is removably mountable in the main assembly of an image forming apparatus. A process cartridge is such a cartridge in which an electrophotographic photosensitive member as an image bearing member, and at least one processing means among a charging means, a developing means, and a cleaning means, which act on the electrophotographic photosensitive member, are integrally disposed, and which is removably mountable in the main assembly of an image forming apparatus. In order for a process cartridge to be compatible with the present invention, a process cartridge must to be provided with a minimum of one toner reception hole similar to the above described ones. <figref idref="DRAWINGS">FIG. 3</figref> shows an example of such a process cartridge, which comprises a frame (housing) formed ordinarily of plastic, and the combination of the photosensitive drum <b>111</b>, developing apparatus <b>100</b>, primary charging device <b>112</b>, and a cleaning means <b>115</b>, which are integrally disposed in the frame.

0066Also in this embodiment, toner is supplied from the toner supply container. However, this embodiment is not intended to limit the scope of the present invention in terms of the particulate consumables supplied by a powder supplying apparatus. For example, the particulate consumables supplied by a powder supplying apparatus may be two-component developer composed primarily of particulate toner and particulate carrier. Obviously, developer may contain a proper amount of ordinary external additive, or the like, for controlling the amount of charge, fluidity, etc., of developer. In other words, all that is necessary for the present invention to be applicable is that a powder supplying apparatus is structured so that it is capable of supplying at least toner.

0067In this specification, the expression that toner is conveyed or dropped virtually in entirety means that the actual amount of the toner conveyed and dropped into an apparatus which is to be supplied with particulate consumables is within the tolerance regarding the theoretical amount by which the apparatus is to be supplied with toner. In other words, it includes the case in which the amount of the toner which fails to be conveyed or dropped is within the tolerance regarding the above-described functions, or negligibly small.

0068Further, the expression that the amount by which toner is conveyed or dropped is practically proportional to the amount by which (number of times, or length of time) the toner conveying members are driven means that the amount by which toner is conveyed or dropped is quantitatively within the tolerance regarding the function of the toner supplying apparatus in terms of supplying toner to an apparatus which is to be supplied with particulate consumables. In other words, it includes the case in which the degree of nonproportionality between the amount by which toner is conveyed or dropped and the amount by which the toner conveying members are driven is negligibly small.

0069In other words, in the present invention, even if a minute amount of toner remains adhering to the internal surface of the second pipe <b>8</b> (second toner chamber), as long as the second toner conveyance screw <b>10</b> (second conveying member) is continuously driven for a length of time long enough for the toner received by the pipe <b>8</b> to be discharged in entirety toward the developing device (third toner chamber), it is assumed that the amount of the toner within the second toner chamber will become zero in a practical sense.

0070The following is another embodiment of the present invention.

0071Instead of placing the first pipe <b>3</b> above the second pipe <b>8</b> as described above, they may be integrated into a single straight pipe, which can be injection molded, and which comprises a first pipe (<b>3</b>) section, in which a first toner conveyance screw equivalent to the above-described first toner conveyance screw <b>5</b> is disposed, and a second pipe (<b>8</b>) section, in which a second toner conveyance screw is disposed. Also in this case, the rotations of the first and second toner conveyance screws are independently controlled as described above.

0072As described above, the above embodiments minimize the amount of the toner which remains in the adjacencies of the toner discharge hole of the second toner chamber, preventing thereby the problem that toner Scatters when the container having the third toner chamber is mounted or dismounted.

0073Further, even if a large amount of toner is delivered in a short time from the first toner chamber to the second toner chamber, the above-described embodiments prevent the toner content in the developing device from locally rising to an extreme level, preventing thereby the formation of an image in nonuniform in density.

0074While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.